1. Technical Filed
The present invention relates to ferroelectric memory devices. In particular, the present invention relates to ferroelectric memory devices with less deterioration caused by fatigue and imprint.
2. Related Art
A conventional ferroelectric memory device is described in Japanese Laid-open Patent Application 2001-76493. The conventional ferroelectric memory device has a dropped voltage power supply circuit that lowers an external power supply, which is structured such that a dropped voltage power supply Vint is supplied to a bit line and a plate line, and a potential Vboot that is stepped up by a threshold voltage Vt of a cell transistor than the dropped voltage power supply Vint or higher is supplied to a word line, whereby deterioration of the ferroelectric characteristics by fatigue and imprint is prevented.
However, because the aforementioned conventional ferroelectric memory device needs to have circuits that generate a dropped voltage power supply and a stepped up voltage power supply, there are problems in that its circuit size becomes larger, and its power consumption increases.
Accordingly, it is an object of the present invention to provide a ferroelectric memory device that can solve the problems described above. The object can be achieved by combinations of characteristics recited in independent claims in the scope of patent claims. Also, dependent claims further define advantageous concrete examples of the present invention.